Here's how you can tell the difference between seals and sea lions, even though the differences are pretty small.
They may look very much alike, but are seals and sea lions related? What are the differences?
Seals and sea lions both belong to the scientific order Pinnipedia. The name literally means "fin-footed." There are 33 living species of pinnipeds. They are all warm-blooded mammals that have a streamlined torpedo body, enabling them to swim and dive gracefully. Both seals and sea lions have flippers that act as rudders, helping them to steer in the water. However, although they are very suited to the marine environment, pinnipeds spend part of their life in the water and part on land, which sets them apart from the other marine mammals (whales). They live a nomadic lifestyle, spending months out at sea and then returning to land to rest. Scientists have divided the pinnipeds into three families: earless seals (Phocidae), eared seals (Otariidae), and walruses (Odobenidae).
The earless seals are the phocids. They are what you would think of as a seal. They are called earless because they lack ear flaps. However, this does not mean they are deaf. Seals have tiny openings, which are called pinnae, that serve as ears. There are eighteen species of seals.
The most distinguished feature of the seal is the flipper. This sets the seal apart from other pinnipeds. They have short foreflippers with a claw on each toe. The hind flippers are also clawed. The flippers have a thin webbing of skin, enabling them to move through the water with grace. Seals can flex their toes to groom themselves or haul themselves out of water. The hind flippers angle toward the rear and cannot be rotated forward. This is a hindrance for seals. For a seal to move across dry land, it must balance its weight on to the fore flippers and crawl along using their bellies.
Seals have more girth than most of the other pinnipeds. They are not as sleek and can even appear chubby. Even though they are disadvantaged on land, they move swiftly through the water. The front flippers serve as rudders for steering. The hind flippers allow the animal to thrust along in the water. It is with these combined adaptations that seals can move along through the water at speeds of 14 to 24 miles an hour.
The sea lion is the pinniped that most individuals know, because they are frequently used in water shows at theme parks. Sea lions make up several of the fourteen species that make up the family Otariidae. The sea lion differs from the seal in that its pinnae are covered by external ear flaps. This is why they are known as the "eared seals." Sea lions also have longer necks than seals. The body of the sea lion is much sleeker than that of the seal, even though sea lions are generally larger than most seals: a male sea lion of certain species can tip the scales at over six hundred pounds, compared to less than four hundred for a large seal.
Another very different adaptation of the sea lions is the flipper. Sea lions' front flippers have only a partial fur covering, unlike the seal, whose flippers are covered entirely by fur. Sea lions' first toes are longer than the other toes. Their hind flippers are extremely flexible, and can actually rotate forward and beneath the body. This enables sea lions to move around on land with ease, unlike the seal. They are very dexterous creatures and thus have been the stars in many movies as well as marine aquarium shows.
Behaviorally, sea lions are usually more vocal than seals. Sea lions are called "sea dogs" due to their unique barking noise, whereas seals tend to make much quieter grunting noises. Sea lions also tend to be more social than other pinnipeds.
Both seals and sea lions have some similarities, such as adaptations that make them extremely effective oceanic animals. Both species are adept at diving and can reach to depths beyond a thousand feet, the record-holder being the elephant seal, which can descend to 4,125 feet. In fact, only the sperm whale and the beluga whale are capable of making deeper dives.
In the wild, both seals and sea lions are hunted by the killer whale. In the past both were also hunted by humans for their pelts and blubber, the fatty insulating layer both groups have beneath their skins.
Seals and sea lions actually have more in common than they have different. The differences are mostly physical as described previously. However, you are more likely to see a sea lion than you are a seal: if you have ever been to San Francisco, you have probably witnessed California Sea Lions piling on top of each other on the docks.